BIO_211_Ch21_Lecture Notes ImmuneSystem

BIO_211_Ch21_Lecture Notes ImmuneSystem - Bio 211 A & P II...

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Bio 211 Ch 21 The Immune System 1 Chapter 21 The Immune System: Innate and Adaptive:Body Defenses Immunity Resistance to disease Immune system has two intrinsic systems Innate (nonspecific) defense system Adaptive (specific) defense system Immunity 1 Innate defense system has two lines of defense First line of defense is external body membranes (skin and mucosae) Second line of defense is antimicrobial proteins, phagocytes, and other cells Inhibit spread of invaders Inflammation is its most important mechanism Immunity 2 Adaptive defense system Third line of defense attacks particular foreign substances Takes longer to react than the innate system Innate and adaptive defenses are deeply intertwined Innate Defenses Surface barriers Skin, mucous membranes, and their secretions Physical barrier to most microorganisms Keratin is resistant to weak acids and bases, bacterial enzymes, and toxins Mucosae provide similar mechanical barriers Surface Barriers Protective chemicals inhibit or destroy microorganisms Skin acidity Lipids in sebum and dermcidin in sweat HCl and protein-digesting enzymes of stomach mucosae Lysozyme of saliva and lacrimal fluid Mucus Surface Barriers Respiratory system modifications Mucus-coated hairs in the nose Cilia of upper respiratory tract sweep dust- and bacteria-laden mucus from lower respiratory passages Internal Defenses: Cells and Chemicals Necessary if microorganisms invade deeper tissues Phagocytes
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Bio 211 Ch 21 The Immune System 2 Natural killer (NK) cells Inflammatory response (macrophages, mast cells, WBCs, and inflammatory chemicals) Antimicrobial proteins (interferons and complement proteins) Fever Phagocytes: Macrophages Macrophages develop from monocytes to become the chief phagocytic cells Free macrophages wander through tissue spaces E.g., alveolar macrophages Fixed macrophages are permanent residents of some organs E.g., Kupffer cells (liver) and microglia (brain) Phagocytes: Neutrophils Neutrophils Become phagocytic on encountering infectious material in tissues Mechanism of Phagocytosis Step 1: Adherence of phagocyte to pathogen Facilitated by opsonization—coating of pathogen by complement proteins or antibodies Mechanism of Phagocytosis Destruction of pathogens Acidification and digestion by lysosomal enzymes Respiratory burst Release of cell-killing free radicals Activation of additional enzymes Oxidizing chemicals (e.g. H2O2) Defensins (in neutrophils) Natural Killer (NK) Cells Large granular lymphocytes Target cells that lack “self” cell-surface receptors Induce apoptosis in cancer cells and virus-infected cells Secrete potent chemicals that enhance the inflammatory response Inflammatory Response Triggered whenever body tissues are injured or infected Prevents the spread of damaging agents
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This note was uploaded on 10/16/2011 for the course SCIENCE Bio 211 taught by Professor Dr.frederickduss during the Spring '11 term at Midlands Tech.

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BIO_211_Ch21_Lecture Notes ImmuneSystem - Bio 211 A & P II...

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